On Thu, Aug 13, 2015 at 04:52:32PM +0000, Philip Downey wrote:
> Hi Andrew
> IGMP snooping is designed to prevent hosts on a local network from receiving
> traffic for a multicast group they have not explicitly joined. Link-Local
> multicast traffic should not have an IGMP client since it is reserved for
> routing protocols. One would expect that IGMP snooping needs to ignore local
> multicast traffic in the reserved range intended for routers since there
> should be no IGMP client to make "join" requests.
The point of this patch is that Linux is sending out group membership
for these addresses, it is acting as a client. What happens with a
switch which is applying IGMP snooping to link-local multicast groups?
You turn on this feature, and you no longer get your routing protocol
messages.
I had a quick look at RFC 3376. The only mention i spotted for not
sending IGMP messages is:
The all-systems multicast address, 224.0.0.1, is handled as a special
case. On all systems -- that is all hosts and routers, including
multicast routers -- reception of packets destined to the all-systems
multicast address, from all sources, is permanently enabled on all
interfaces on which multicast reception is supported. No IGMP
messages are ever sent regarding the all-systems multicast address.
IGMP v2 has something similar:
The all-systems group (address 224.0.0.1) is handled as a special
case. The host starts in Idle Member state for that group on every
interface, never transitions to another state, and never sends a
report for that group.
But i did not find anything which says all other link-local addresses
don't need member reports. Did i miss something?
Andrew
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